9,198 research outputs found
Source power estimation for array processing applications under low sample size constraints
Copyright © 2008 IEEE. All Rights Reserved.This paper proposes a new power estimation technique for array processing applications in the low sample size regime. The technique is especially suitable for applications where the direction of arrival (DoA) detection is performed using subspace identification techniques, because the eigenvalues and eigenvectors of the sample covariance matrix are already computed for DoA estimation and are therefore available for power estimation as well. The performance of the algorithm is similar to that of the traditional maximum likelihood (ML) power estimation technique, but it is more robust to the presence of outliers in the direction of arrival (DoA) detection process. This is because, contrary to the ML estimator, the proposed power estimator only depends on the signature of the source of interest.Mestre, X., Johnson, B.A. and Abramovich, Y.I
Investigation of a Thin Wing of Aspect Ratio 4 in the Ames 12-foot Pressure Wind Tunnel III : the Effectiveness of a Constant-chord Aileron
A \u3cem\u3eDendroctonus\u3c/em\u3e Bark Engraving (Coleoptera: Scolytidae) From A Middle Eocene \u3cem\u3eLarix\u3c/em\u3e (Coniferales: Pinaceae): Early Or Delayed Colonization?
An engraving made by a scolytid bark beetle, assigned to the genus Dendroctonus of the tribe Tomicini, has been identified on a mummified, middle Eocene (45 Ma) specimen of Larix altoborealis wood from the Canadian High Arctic. Larix altoborealis is the earliest known species of Larix, a distinctive lineage of pinaceous conifers that is taxonomically identifiable by the middle Eocene and achieved a broad continental distribution in northern North America and Eurasia during the late Cenozoic. Dendroctonus currently consists of three highly host-specific lineages that have pinaceous hosts: a basal monospecific clade on Pinoideae (Pinus) and two sister clades that consist of a speciose clade associated exclusively with Pinoideae and six species that breed overwhelmingly in Piceoideae (Picea) and Laricoideae (Pseudotsuga and Larix). The middle Eocene engraving in L. altoborealis represents an early member of Dendroctonus that is ancestral to other congeneric species that colonized a short-bracted species of Larix. This fossil occurrence, buttressed by recent data on the phylogeny of Pinaceae subfamilies and Dendroctonus species, indicates that there was phylogenetically congruent colonization by these bark-beetle lineages of a Pinoideae + (Piceoideae + Laricoideae) host-plant sequence. Based on all available evidence, an hypothesis of a geochronologically early invasion during the Early Cretaceous is supported over an alternative view of late Cenozoic cladogenesis by bark beetles onto the Pinaceae. These data also suggest that host-plant chemistry may be an effective species barrier to colonization by some bark-beetle taxa over geologically long time scales
Dynamics of Multi-Player Games
We analyze the dynamics of competitions with a large number of players. In
our model, n players compete against each other and the winner is decided based
on the standings: in each competition, the mth ranked player wins. We solve for
the long time limit of the distribution of the number of wins for all n and m
and find three different scenarios. When the best player wins, the standings
are most competitive as there is one-tier with a clear differentiation between
strong and weak players. When an intermediate player wins, the standings are
two-tier with equally-strong players in the top tier and clearly-separated
players in the lower tier. When the worst player wins, the standings are least
competitive as there is one tier in which all of the players are equal. This
behavior is understood via scaling analysis of the nonlinear evolution
equations.Comment: 8 pages, 8 figure
Local Guarantees in Graph Cuts and Clustering
Correlation Clustering is an elegant model that captures fundamental graph
cut problems such as Min Cut, Multiway Cut, and Multicut, extensively
studied in combinatorial optimization. Here, we are given a graph with edges
labeled or and the goal is to produce a clustering that agrees with the
labels as much as possible: edges within clusters and edges across
clusters. The classical approach towards Correlation Clustering (and other
graph cut problems) is to optimize a global objective. We depart from this and
study local objectives: minimizing the maximum number of disagreements for
edges incident on a single node, and the analogous max min agreements
objective. This naturally gives rise to a family of basic min-max graph cut
problems. A prototypical representative is Min Max Cut: find an cut
minimizing the largest number of cut edges incident on any node. We present the
following results: an -approximation for the problem of
minimizing the maximum total weight of disagreement edges incident on any node
(thus providing the first known approximation for the above family of min-max
graph cut problems), a remarkably simple -approximation for minimizing
local disagreements in complete graphs (improving upon the previous best known
approximation of ), and a -approximation for
maximizing the minimum total weight of agreement edges incident on any node,
hence improving upon the -approximation that follows from
the study of approximate pure Nash equilibria in cut and party affiliation
games
Parameterized Model-Checking for Timed-Systems with Conjunctive Guards (Extended Version)
In this work we extend the Emerson and Kahlon's cutoff theorems for process
skeletons with conjunctive guards to Parameterized Networks of Timed Automata,
i.e. systems obtained by an \emph{apriori} unknown number of Timed Automata
instantiated from a finite set of Timed Automata templates.
In this way we aim at giving a tool to universally verify software systems
where an unknown number of software components (i.e. processes) interact with
continuous time temporal constraints. It is often the case, indeed, that
distributed algorithms show an heterogeneous nature, combining dynamic aspects
with real-time aspects. In the paper we will also show how to model check a
protocol that uses special variables storing identifiers of the participating
processes (i.e. PIDs) in Timed Automata with conjunctive guards. This is
non-trivial, since solutions to the parameterized verification problem often
relies on the processes to be symmetric, i.e. indistinguishable. On the other
side, many popular distributed algorithms make use of PIDs and thus cannot
directly apply those solutions
Are megaquakes clustered?
We study statistical properties of the number of large earthquakes over the
past century. We analyze the cumulative distribution of the number of
earthquakes with magnitude larger than threshold M in time interval T, and
quantify the statistical significance of these results by simulating a large
number of synthetic random catalogs. We find that in general, the earthquake
record cannot be distinguished from a process that is random in time. This
conclusion holds whether aftershocks are removed or not, except at magnitudes
below M = 7.3. At long time intervals (T = 2-5 years), we find that
statistically significant clustering is present in the catalog for lower
magnitude thresholds (M = 7-7.2). However, this clustering is due to a large
number of earthquakes on record in the early part of the 20th century, when
magnitudes are less certain.Comment: 5 pages, 5 figure
Association between Participation in Outpatient Cardiac Rehabilitation and Self-Reported Receipt of Lifestyle Advice from a Healthcare Provider: Results of a Population-Based Cross-Sectional Survey
We test the hypothesis that the odds of self-reported receipt of lifestyle advice from a health care provider will be lower among outpatient cardiac rehabilitation (OCR) nonattendees and nonreferred patients compared to OCR attendees. Logistic regression was used to analyse cross-sectional data provided by 65% (4971/7678) of patients aged 20 to 84 years discharged from public hospitals with a diagnosis indicating eligibility for OCR between 2002 and 2007. Among respondents, 71% (3518) and 55% (2724) recalled advice regarding physical activity and diet, respectively, while 88% (592/674) of smokers recalled quit advice. OCR attendance was low: 36% (1764) of respondents reported attending OCR, 11% (552) did not attend following referral, and 45% (2217) did not recall being invited. The odds of recalling advice regarding physical activity and diet were significantly lower among OCR nonattendees compared to attendees (OR 0.34, 95% CI 0.21, 0.56 and OR 0.33, 95% CI 0.25, 0.44, resp.) and among nonreferred respondents compared to OCR attendees (OR 0.10, 95% CI 0.07, 0.15 and OR 0.17, 95% CI 0.14, 0.22, resp.). Patients hospitalised for coronary heart disease should be referred to OCR or a suitable alternative to improve recall of lifestyle advice that will reduce the risk of further coronary events
Association between Participation in Outpatient Cardiac Rehabilitation and Self-Reported Receipt of Lifestyle Advice from a Healthcare Provider: Results of a Population-Based Cross-Sectional Survey
We test the hypothesis that the odds of self-reported receipt of lifestyle advice from a health care provider will be lower among outpatient cardiac rehabilitation (OCR) nonattendees and nonreferred patients compared to OCR attendees. Logistic regression was used to analyse cross-sectional data provided by 65% (4971/7678) of patients aged 20 to 84 years discharged from public hospitals with a diagnosis indicating eligibility for OCR between 2002 and 2007. Among respondents, 71% (3518) and 55% (2724) recalled advice regarding physical activity and diet, respectively, while 88% (592/674) of smokers recalled quit advice. OCR attendance was low: 36% (1764) of respondents reported attending OCR, 11% (552) did not attend following referral, and 45% (2217) did not recall being invited. The odds of recalling advice regarding physical activity and diet were significantly lower among OCR nonattendees compared to attendees (OR 0.34, 95% CI 0.21, 0.56 and OR 0.33, 95% CI 0.25, 0.44, resp.) and among nonreferred respondents compared to OCR attendees (OR 0.10, 95% CI 0.07, 0.15 and OR 0.17, 95% CI 0.14, 0.22, resp.). Patients hospitalised for coronary heart disease should be referred to OCR or a suitable alternative to improve recall of lifestyle advice that will reduce the risk of further coronary events
Circuits in random graphs: from local trees to global loops
We compute the number of circuits and of loops with multiple crossings in
random regular graphs. We discuss the importance of this issue for the validity
of the cavity approach. On the one side we obtain analytic results for the
infinite volume limit in agreement with existing exact results. On the other
side we implement a counting algorithm, enumerate circuits at finite N and draw
some general conclusions about the finite N behavior of the circuits.Comment: submitted to JSTA
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